An additional carrier type has been extensively discussed for the Radio Layer 1 (RAN1) of the 3rd Generation Partnership Project (3GPP) collaboration between various telecommunications associations. From the perspective of RAN1, the main motivations for introducing a New Carrier Type (NCT) for carrier aggregation include enhanced spectral efficiency, improved support for heterogeneous network, and energy efficiency.
The baseline approach for the Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS) mapping for the NCT is as per Release 8 (Rel-8) of the 3GPP Mobile Broadband Standard. That is, the PSS/SSS signals for the NCT are mapped onto the last and the next to last Orthogonal Frequency Division Multiplexing (OFDM) symbols in the center six Physical Resource Blocks (PRBs) of the system bandwidth in the first slot of subframes 0 and 5 according to the 3GPP TS 36.211. While the baseline approach is simplest in terms of specification impact and UE implementation, a Demodulation Reference Signal (DMRS) (also referred to as a User Equipment-Specific Reference Signal for Demodulation (UE-RS)) and PSS/SSS collision issue will occur, as illustrated in FIGS. 1A and 1B. FIG. 1A depicts a Physical Resource Block (PRB) for a Frequency-Division Duplexing (FDD) system, and FIG. 1B depicts a PRB for a Time-Division Duplexing (TDD) system. A collision occurs when the PSS/SSS signals overlap with the DMRS signals, as depicted by boxed Resource Elements (REs) in the PRBs.
Release 10 (Rel-10) of the 3GPP Standard does not allow UE-RS-based transmission schemes in the center six PRBs in subframes 0 and 5 in which PSS/SSS signals are transmitted because the UE-RS signal mapping collides with the legacy PSS/SSS signal mapping at symbols 5 and 6. In other words, demodulation of Rel-10 uses Cell Specific Reference Signal (CRS) based transmission modes if such collisions occur and the US-RS is not used. In Release 11 (Rel-11) of the 3GPP Standard, the New Carrier Type (NCT) can carry one Reference Signal (RS) port (consisting of the Rel-8 CRS Port 0 Resource Elements (REs) per PRB and the Rel-8 sequence) within one subframe with 5 ms periodicity and this RS port (based on Rel-8 CRS port) is not used for demodulation.
It will be appreciated that for simplicity and/or clarity of illustration, elements depicted in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. The scaling of the figures does not represent precise dimensions and/or dimensional ratios of the various elements depicted herein. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements.